Abstract

This study presents an analysis of a severe weather case that took place
during the early morning of the 2nd of November 2008, when intense
convective activity associated with a rapidly evolving low pressure system
affected the southern coast of Catalonia (NE Spain). The synoptic
framework was dominated by an upper level trough and an associated cold
front extending from Gibraltar along the Mediterranean coast of the Iberian
Peninsula to SE France, which moved north-eastward. South easterly winds
in the north of the Balearic Islands and the coast of Catalonia favoured high
values of 0-3 km storm relative helicity which combined with moderate
MLCAPE values and high shear favoured the conditions for organized
convection. A number of multicell storms and others exhibiting supercell
features, as indicated by Doppler radar observations, clustered later in a
mesoscale convective system, and moved north-eastwards across Catalonia.
They produced ground-level strong damaging wind gusts, an F2 tornado,
hail and heavy rainfall. Total lightning activity (intra-cloud and cloud to
ground flashes) was also relevant, exhibiting several classical features such
as a sudden increased rate before ground level severe damage, as discussed
in a companion study. Remarkable surface observations of this event include
24 h accumulations exceeding 100 mm in four different observatories and
30 minute rainfall amounts up to 40 mm which caused local flash floods. As
the convective system evolved northward later that day it also affected SE
France causing large hail, ground level damaging wind gusts and heavy
rainfall.